This invention relates to continuous glass-reinforced engineering thermoplastic polyurethane sheets. A major drawback in the continuous production of glass reinforced thermoplastic sheets (also known as glass mat thermoplastics or GMT) is the inefficiency of impregnating the layer of glass fiber with the viscous thermoplastic layer. Consequently, somewhat complex methods requiring the use of additional extruders have been devised to promote fiber impregnation, such as the method disclosed by Degginger et al. in U.S. Pat. No. 4,098,943.
To address in part the deficiencies of Dregginger et al., Segal et al, in U.S. Pat. No. 4,469,543 discloses a method for continuously laminating a thermoplastic layer that is reinforced with fiber filler to a glass fiber mat reinforcing layer, wherein the glass fiber is thoroughly impregnated with thermoplastic resin. The impregnation is achieved by laminating between each reinforced layer/glass-fiber mat interface a layer of non-filled thermoplastic polymer that is compatible with the thermoplastic polymer of the reinforced layer. In a preferred embodiment of the invention, the thermoplastic is a polyamide.
Nevertheless, efficient and effective impregnation of resin into a glass mat remains a challenge. It would therefore be an advance in the art of GMT to discover a resin that can wet out the glass fibers in a glass mat completely and efficiently.
The present invention addresses a need in the art by providing a glass mat thermoplastic comprising a glass mat impregnated with an engineering thermoplastic polyurethane having a Tg of at least 50xc2x0 C.
In a second aspect, the present invention is a process for preparing a glass mat thermoplastic comprising the steps of a) contacting a continuous glass mat with an engineering thermoplastic polyurethane (ETPU) film or sheet with sufficient pressure and heat to form a multilayered structure which contains a wetted out glass mat layer sandwiched between an ETPU layer and a glass mat layer, wherein the ETPU layer has a Tg of at least 50xc2x0 C.; b) thermoforming or compression molding the multilayered structure with sufficient heat to substantially completely wet out the glass mat with the ETPU; and c) cooling the substantially wetted out thermoformed glass mat to a temperature below the Tg of the ETPU.
In a third aspect, the present invention is a process for preparing a glass mat thermoplastic comprising the steps of a) contacting a continuous glass mat between a first engineering thermoplastic polyurethane (ETPU) film or sheet and a second engineering thermoplastic polyurethane film or sheet with sufficient pressure and heat to form multilayered partially wetted out glass mat, wherein the ETPU layer has a Tg of at least 50xc2x0 C.; b) thermoforming or compression molding the partially wetted out glass mat with sufficient heat to substantially completely wet out the glass mat with the ETPU; and c) cooling the substantially wetted out thermoformed glass mat to a temperature below the Tg of the ETPU.